O Scale Track Grades

My maximum grade is 2%, and, in my opinion, that's plenty.  You could, theoretically, build a 4% grade on your layout, but even model couplers do not like grades of that severity.  Personally, I would say that Atlas locomotives ought to be able to handle the job, as they are almost bullet-proof in durability.  However, just like real trains, they will pull fewer cars on severe grades, and you will have to check them periodically for heat.

One thing to consider -- and this is important -- is the transition into and out of grade.  The more severe the grade, the longer the transition needs to be.  If the transition is too short, your trains will be uncoupling due to coupler vertical bypass, and this will be experienced more often on long cars.  I have cars from several manufacturers, and there is not great consistency in coupler height.  Even with a 2% grade, I occasionally experience a train separation when a train is passing through the transition section.

Well said, Tom.

Even grades of 3% are OK - on the straight.  Curves introduce more friction at the rails and exacerbate the degree of difficulty.

Thanks for the info guys.

A couple of possibly relevant threads based on Rich Trow's layout.  He has some steep grades in and out of staging.

Rail profile

Grade test

I have a grade that is about 3 3/4% or maybe a little more going up a short branch to mine.     It is also on a 48 inch radius curve.    One loco (USH I1 2-10-0) can handle about 14-15 Atlas O H21 hoppers.    The train is about 18-19, it takes two locos.   No kinks in the track or you gtet a derailment where it pushes cars out of the curve because of weight.

Wow, Rich has gone as steep as 7% successfully to get out of his staging yard. That is using 3 rail and single locos with traction tyres pulling 12 autoracks. I'm guessing two 2 rail Atlas locos, twelve 40 and 50 foot cars and two helper locos behind the caboose should handle 4.5% even on a 48" radius curve.

3.8%   8" difference in levels requires 12' to 16' of run. Tough to get it straight, on a small layout.

There are two sections of the outside track, about 3 to 4 feet each that are not  involved in the grades.

If the transition is too sharp the pilot (cow catcher) on a die cast steam locomotive can short out on the center rail/

Also, it is the combination of rise and length of a grade and not just the grade.  You can climb a much steeper grade if it's short enough as Rich has demonstrated.  Only a portion of the total train is on the grade at any time.

The theoretical limiting grade for a locomotive with all wheels powered for steel wheels on steel rails in 25%.

Jan

% Grade = Rise/Run X 100  

I had a Sunset B&O T3 (2 rail) running on a 2% or less grade but 6 walthers passenger cars caused it to slip.  I added weigh to the boiler and then we made it to the top.  6 walthers cars with walthers trucks is pretty heavy.  Heavy engines and light trains are big variables but  4% is pretty steep for most engines.  I am building a new layout and have a long 1.5% grade along two walls.   But even with that, I kept the curve portion in the middle of the grade level. 

Mike that's a very good looking layout.

I kept grades to 2%. Even then, my greatest difficulty was with scale 21" passenger cars. The Kadees would decouple on the transition. I had to ease into the grade to stop that happening. Not a problem for shorter freight cars but scale auto racks exhibited the same problem. 

I have a 2% grade on my layout...for longer passenger trains I need 3 Sunset F7 locos to keep from slipping as they have no traction tires.  I carefully watched the couplers for vertical sliding between cars as they transversed the hill, and adjusted the risers accordingly.  Sometimes screwing a 1x4 underneath the roadbed creating a "T" cross-section for rigidity.  My Atlas MP15 was unable to make it with a 3-car set of diecast Maxi-stacks.  I may need to add some weights on the inside of that loco for ballist.